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United States Patent | 5,608,514 |
Stann ,   et al. | March 4, 1997 |
In a high range resolution ladar, a chirp signal waveform is propagated as a divergent laser light waveform and the target reflected return is collected and converted to a current proportional to power. An undelayed chirp signal is added in a mixer to the return current and then low pass filtered to recover a mixed intermediate frequency (IF) signal having a frequency proportional to the target range. Periodically, the light circuit is interrupted and the chirp signal is processed through the mixer and low pass filter without a target return current and this output, the mixer self-clutter, is stored. This stored self-clutter signal is subsequently subtracted from the mixed IF signal on a chirp by chirp basis to cancel the self-clutter produced by the mixer. The subtracted signal is then frequency analyzed to determine target range.
Inventors: | Stann; Barry L. (Silver Spring, MD); Ruff; William C. (Baltimore, MD); Sztankay; Zoltan G. (Rockville, MD) |
Assignee: | The United States of America as represented by the Secretary of the Army (Washington, DC) |
Appl. No.: | 424949 |
Filed: | April 19, 1995 |
Current U.S. Class: | 356/5.09; 342/128; 342/159; 356/5.12; 356/5.13 |
Intern'l Class: | G01C 003/08; G01S 013/08 |
Field of Search: | 356/5.09,5.12,5.13 342/128,159 |
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"Characterization of a Scannerless LADAR System", Phil Garcia et al, SPIE l. 1936 Applied Laser Radar Technology (1993), pp. 23-30. "Non-scanned LADAR Imaging and Applications", John P. Anthes et al, SPIE vol. 1936 Applied Laser Radar Technology (1993), pp. 11-22. "Short Range Target Detection Using A Modulated CW Laser Diode", William C. Ruff, Thesis submitted to the Faculty of the Graduate School of the University of Maryland in partial fulfillment of the requirements for the degree of Master of Science, 1991. "A Practical Low-Cost High-Range-Resolution Ladar", Barry L. Stann, William C. Ruff and Zoltan G. Sztankay, Department of the Army, Army Research Laboratory, Adelphi, Maryland. |